Wednesday, December 1, 2010

In today's class, we first went over the worksheets COULOMB'S LAW (the one where you had to underline the right answer) and ELECTRICAL FORCES.

For COULOMB'S LAW the answers are:
1-b. attraction
1-c. greater, less, 1/4 as much
2-a. doubled
2-b. quadrupled
2-c. quadrupled
2-d. 16 times

For ELECTRICAL FORCES the answers are:
1. -3.6 x 10^10 N (use Fe=kq1q2/R^2)
2-a. 7.80 x 10^-47 N (use Fg=GMm/R^2)
2-b. 8.80 x 10^-8 N (use Fe=kq1q2/R^2)
3. 2.5 x 10^19 electrons (use charge/e)
4. -1.76 x 10^8 C (use given mass/mass of electron)
5-a. 1.76 x 10^-15 N (add the force of each charged objects)
5-b. 2.63 x 10^11 m/s^2 (use a=Fnet/m)

Next we read through our first handout Coulomb's Law in One Dimension, Two Dimensions: Equilateral Triangle, and Two Dimensions: The Square.

To solve problems in one dimension, simply add the charges (like vectors). Don't forget that like charges repel and unlike charges attract.

To solve problems in two dimensions, first find the x and y components of each charge and add them together. Then combine the totaled x and y components by using the pythagorean theorem.

** Like vectors, electrical forces have direction.

Lastly, we were given question 5 on page 420 and questions 15, 16 and 19 on page 423 of the green books for homework!